1. Field of the Invention
The present invention relates to a tool, in particular a rotationally driven cutting tool, and in particular a cutting tool for the fine machining of workpieces.
2. Description of the Related Art
Cutting tools, in particular for the fine machining of workpieces, in which at least one cutting insert, fastened so as to be removable, is provided on a tool element, have long been known, for example from DE 38 03 188 A1. The cutting insert, in the form of a polygon plate, is thereby seated in a correspondingly formed pocket of the blade bearer, and is pressed flatly or in planar fashion against a base surface of the pocket by a clamping screw that penetrates the cutting insert essentially centrically.
So that, after the cutting insert has been installed, a precise positional fixing and orientation of the functional edges of the tool is possible in relation to the axis of rotation, such tools are often equipped with a fine adjustment device. The cutting insert is thereby supported with a lateral wall against an adjusting element that can be displaced relative to the cutting insert with the aid of an adjusting or set screw arrangement. Such fine adjustment devices are known for example from DE 195 21 599 A1, from JP 10-277839 A, from U.S. Pat. No. 3,662,444, or from DE 42 43 586 A1. Instead of an adjusting screw, an adjusting eccentric has also already been used, as is known for example from DE 29 48 250 C2.
A tool as recited below is known from DE 100 60 283 C1. The adjusting element is thereby formed by an adjusting bored part that has a continuous inner winding and is supported via a semicylindrical outer surface of a corresponding opening in the blade bearer. The adjusting screw arrangement is formed by a differential screw whose outer threading, having a first orientation, engages with the inner threading of the adjusting element, and whose threaded segment, having a second orientation, engages with a threaded bore in the blade bearer. The differential screw can alternatively be actuated either from the side of the cutting insert or, if the threaded bore in the blade bearer is fashioned as a through bore, from the side of the screw part that engages with the blade bearer.
With this known fine adjustment device, it is certainly possible to carry out the required adjustments of the cutting insert, said adjustments serving mainly for the reliable compensation of manufacturing tolerances at the cutting insert and/or at the receiving pocket. However, it has turned out that the design of the known fine adjustment device requires a relatively expensive machining of the blade bearer. This has a negative effect in particular if the tools have a relatively small nominal diameter, or for example if particularly difficult-to-cut materials are used for the blade bearer.
The present invention is therefore based on the object of developing a tool according to the below discussion in such a way that a fine adjustment of the cutting insert can be realized even for tools having the smallest nominal diameter, while providing an economical manufacturing method, even if materials that are particularly difficult to cut, such as for example hard materials, are used in the area of the blade bearer. This object is achieved by the features of the below claims.
According to the present invention, a threaded sleeve o: bushing of the adjustment screw arrangement is placed loosely in a through opening in the blade bearer. Because of the loose placement of the threaded sleeve, the through opening can be formed so as to be smooth on the inside. The threaded sleeve is placed into the through opening from the side facing the cutting insert, and is supported at the narrow point in such a way that the adjusting screw arrangement remains capable of being actuated through the narrow point. This design makes it possible to form the inner through opening in the blade bearer as simply as possible, for example as a smooth cylindrical opening. The fine adjustment device can thus be used even for tools having a very small nominal diameter, without having to accept a significant cutting expense in the machining of the blade bearer. The through opening, smooth on the inside, can be manufactured very economically, even if very difficult-to-cut materials are used on the sides of the blade bearer. These are for example hard materials such as carbide, nitride, or boride, or also nonmetallic hard materials and hard materials systems, as are known for example in the form of mixed carbides, carbon nitrides, carbide-boride combinations, or as mixed ceramics and nitride ceramics. Hard materials of this sort are often sintered materials. The construction according to the present invention of the fine adjustment device even makes it possible to create the through opening in the blade bearer already before the final sintering process, for example already during the compression molding process or after a pre-sintering method step. This is possible because the adjusting screw arrangement is placed loosely in the through opening of the blade bearer, so that dimensional and/or tolerance deviations with respect to the position and shape of the inner through opening cannot effectively have an adverse effect on the functioning of the fine adjustment device. In this way, the design according to the present invention results in the particular additional advantage that when the cutting insert has been installed the components of the fine adjustment device are held in captive fashion in the through opening of the blade bearer, underneath the cutting insert. Even given a loosening of the preloading force of the adjusting element, which can be caused for example by vibrations of the tool, it is ensured that no components of the fine adjustment device can be lost.
A particular advantage of the tool according to the present invention is that the fine adjustment device for the cutting insert claims very little constructive space, thus creating the possibility that, even in the embodiment having small nominal diameters, the tool can be equipped with standardized (DIN/ISO) indexable inserts. Down to nominal diameters of 12 mm, standardized indexable inserts (for example size 04) can be used, while at larger nominal diameters (for example, 16 mm), correspondingly larger standardized indexable inserts can be used, for example size 06. In addition, the inventors were able to manufacture tools having a nominal diameter of 6 and 5 mm, and to carry out the fine adjustment of the cutting insert by using a threaded sleeve having a thread dimension of M1.2 or M0.8 respectively.
Advantageous developments of the present invention are the subject matter of the subclaims. One development is particularly suited for extremely small dimensioning of the fine adjustment device, for example for tools having a nominal diameter of less than 16 mm. It has turned out that with threaded sleeve diameters of less than 2 mm, pressure forces can easily be exerted on the screw or threaded bolt, and thus on the adjusting element, that are sufficient for the fine adjustment of the blade(s) even if the cutting insert is completely fastened in the pocket. The inner threading of the threaded sleeve can even be manufactured easily in the range down to M0.8, because the selection of material for the components of the fine adjustment device is independent of the material of the cutting insert and/or of the blade bearer.
An advantageous alternative for the construction is represented by the below-described development that is advantageously to be used if tools having a larger nominal diameter are equipped with a fine adjustment device according to the present invention. For an essentially rotationally fixed accommodation of the threaded sleeve in the through opening, a solder or glue connection can be used. However, it is equally possible for the rotational securing of the threaded sleeve to be provided by a special shaping of the sleeve cross-section on the one hand and of the cross-section of the through opening on the other hand.
In this variant, it is advantageous to select the inner width of the narrow point smaller than the outer diameter of the screw bolt that is screwed into the threaded sleeve, so that protection against loss is provided.
The developments according to others of the claims are provided in order to influence the transmission of force from the fine adjustment device to the cutting part as advantageously as possible. These developments make it possible to further reduce the dimensions of the fine adjustment device, and thus to equip tools having a still smaller nominal diameter with the fine adjustment device according to the present invention, in particular if, as a material for the blade bearer, a hard metal is used, or another hard material, or a material having significantly greater strength and therefore significantly greater resistance to cutting.
The development of another claim improves the flow of force to the blade bearer, and minimizes the contact stresses that can have a critical effect in particular with the use of hard materials.
If the cutting insert of the tool is formed by an indexable insert, it is advantageous if the adjusting element is supported on a flank or free surface of the indexable insert. In this way, not only is the cutting edge protected, but the bevel of the flank is also advantageously used as a component of a wedge drive for a deflection of force and amplification of force.
In principle, the realization according to the present invention of the fine adjustment device is not limited to a particular geometry of the pocket in the blade bearer or of the cutting insert. However, with another of the developments, there results a particularly well-defined positional adjustment of the cutting insert with the best possible protection of the cutting insert on the one hand and of the blade bearer on the other hand.
The through opening provided in the blade bearer for accepting the adjusting screw arrangement can be oriented arbitrarily with respect to the base surface of the pocket of the blade bearer, and can for example also be oriented parallel to the base surface of the pocket. However, if, the through opening has an extension that is set at an angle to the base surface of the pocket of the blade bearer, there results the particular advantage that the bevel of the flank can also be used for force deflection and force transmission.
There is also no limitation in principle for the shape of the cross-section of the through opening in the blade bearer. The decisive advantage from the manufacturing point of view, in particular with the use of high-strength materials in the area of the blade bearer, results from the fact that the inner surface of the opening need comprise no undercuts, and that only very low demands need be made on the dimensional accuracy of the inner through opening, because the adjusting screw arrangement is housed in the through opening with a degree of play. Particular manufacturing-related advantages result from yet another development. Such an opening can even be formed, with the sufficient low dimensional accuracy and rough positional tolerance, in the tool bearer, if this bearer is for example made of a sintered material. The positional and dimensional precision that can be achieved thereby is easily sufficient to accommodate the adjustment screw arrangement, having arbitrary dimensions, in the through opening in a captive fashion that is nevertheless reliably accessible from the outside.
The narrow point in the through opening can also be made in various ways, such as for example by driving in a transverse pin that protrudes into the opening. However, a particularly simple and effective construction results according to another development. According to this development, if the inner through opening is made in the molding process, i.e., during the pressing process of the blade bearer made of a hard material, all subsequent machining after the sintering process can be omitted.
Moreover, advantageous materials are indicated for the blade bearer and/or the cutting insert, with which the advantages of the inventive construction are utilized especially well. However, it is to be noted that the present invention is not limited to this choice of materials.
At least some selected functional surfaces of the tool and/or of the fine adjustment device, preferably in those areas that are exposed to increased wear, can, in order to improve durability, be provided at least in some areas, such as for example in the area of the blades or in the area of the force-transmitting contact surfaces, with a coating that is preferably realized as a hard material layer. This can for example be a layer of diamond, preferably nanocrystalline diamond, of titanium nitride, or of titanium aluminum nitride. Advantageous realizations of the coating form the subject matter of others of the claims.
Additional advantageous realizations of the present invention form the subject matter of the subclaims.
In the following, exemplary embodiments of the present invention are explained in more detail on the basis of schematic drawings.